The present invention relates to a radio wave absorber for absorbing radio waves of a microwave band or a millimetric wave band, and more particularly, to a radio wave absorber that can obtain high radio wave absorption characteristics in a wide frequency range.
Radio wave absorbers are widely used for marine vessels, aircraft, etc. Such a radio wave absorber absorbs radio waves emitted from one""s radar and lowers the reflected radio waves to be returned to the radar, so that the presence can not be easily detected by the radar.
In recent years, studies for use of radio waves of a microwave band and a millimetric wave band have been briskly carried out in various fields. Such radio waves of a microwave band and a millimetric wave band might damage human bodies and equipment. Therefore, with the aforementioned studies, radio wave absorbers have been receiving public attention, as one of means for preventing radio wave interferences.
Conventionally, the radio wave absorber mentioned above comprises a radio wave reflecting plate and an radio wave absorbing layer, provided thereon, consisting of a single layer matching with the frequency of radio waves to be absorbed. The radio wave absorber of so-called xe2x80x9cmatching type absorptionxe2x80x9d, for absorbing radio waves by using such a radio wave absorbing layer consisting of a single layer, as shown in FIG. 6, has a high radio wave absorption capacity in a frequency range before and after one frequency f. However, on the contrary, the frequency range to be absorbed is limited in a narrow range. As a result, it can not apply to fields other than those of marine vessels, aircraft, etc.
It is an object of the present invention to provide a radio wave absorber that can attain a high radio wave absorption capacity in a frequency range wider than before.
In order to achieve the aforementioned object, the radio wave absorber of the present invention is characterized by comprising a radio wave reflector and at least two radio wave absorbing layers disposed on a surface of the radio wave reflector, the at least two radio wave absorbing layers being formed of a base material and electroconductive titanium oxide blended therewith, and having different blend ratios of the electroconductive titanium oxide so as to make their radio wave absorption property different.
According to the radio wave absorber of the present invention, it becomes possible to obtain high radio wave absorption characteristics in a frequency range before and after each of the at least two frequencies. Therefore, a high radio wave absorption capacity can be achieved in a frequency range wider than the conventional radio wave absorber with a radio wave absorbing layer consisting of a single layer.